1. Field of the Invention
The present invention relates to an optical recording medium, an optical recording method, an optical reproducing method, an optical recording apparatus, and an optical reproducing apparatus. More particularly, the present invention is suitable for use in the case where information is recorded and reproduced based on a change in reflectance.
2. Description of the Related Art
Up to now, optical recording media such as a compact disc (CD) and a compact disc-recordable (CD-R) have been developed and commercialized. Of the optical recording media, the CD is a reproduction-only optical disc on which a pit train is spirally formed. Information is read out from the CD based on a change in intensity of reflection light when a pit is irradiated with laser light. The CD-R is a recordable optical disc in which organic pigment is used as a material of the recording layer. A groove is spirally formed on the disc surface of the CD-R. The groove is irradiated with high-power laser light to deform or alter a part of the recording layer, thereby recording information therein. In addition to the optical recording media, a digital versatile disc (DVD) using red laser light as laser light for recording and reproducing has been commercialized. Further, the standardization of a next-generation DVD using blue laser light as laser light for recording and reproducing proceeds and the next-generation DVD are being commercialized.
In the reproduction-only optical disc among the above-mentioned optical discs, a pit train having a length corresponding to a recording signal is formed in a track shape. In the recordable optical disc, the recording layer is deformed or altered to form a pit train having a length corresponding to a recording signal on the groove. In either type of the optical discs, a single mark is formed from a single pit.